Brain
and Central Nervous System Tumors

Cancers of the central
nervous system are the second most common form of cancer in children and the
most common type of solid tumor (1). These cancers may involve
both the spinal cord or brain.

Causes of these cancers
are largely unknown, though some studies suggest that chemical exposures may
be a cause. These cancers are most common in children under age seven (2). Boys are more likely to have
central nervous system tumors than girls (3).

Brain cancers are one of
the cancers that are increasing in children. From 1973 to 1994, the number
of reported brain cancers in children under 15 increased 1.8% per year (3).

Some argue that the increase
actually represents improved detection of the cancer, possibly through use of
MRI (magnetic resonance imaging) (4, 5). Many other
top scientists disagree. They rgue that the increase in cases is real because
brain tumors do not go undetected, regardless of the method used (6).
Moreover, the increase appears to be continuing and not leveling off (7). If part of the increase were
due to improved methods that find cases earlier, one would expect to see a reduced
rate later. This does not appear to have occurred.

Unfortunately, the improvements
in treatments that have occurred for many childhood cancers have not been achieved
for brain cancer. The proportion of cancer deaths in children due to brain
cancer has doubled in the last 25 years (7).
The quality of life of survivors of central nervous system cancers may also
be worse than that of other common kinds of childhood cancer.

Ionizing radiation
is considered an established cause of brain tumors in children (3,
8).

Other environmental agents
that have been suggested as contributing to this type of cancer include pesticides,
solvents, and certain compounds called N nitroso compounds that are found
in cured meats such as bacon, ham, and sausages (9).

There is some evidence
that exposure to pesticides may be linked to brain tumors, though only
a few studies have looked at this.

·A recent review of studies that looked at pesticides and childhood
cancer found that nine of the 17 studies reported increased risk of brain
cancer to be associated with pesticide exposure (10). Five studies found a positive
relationship that was not strong enough to be reported as being statistically
significant. Three studies found no excess risk to be associated with pesticide
exposure.

·A large study of cancer in the children of farmers in Norway
found that children of parents who used pesticides had a three times higher
risk for certain types of brain tumors (11).

·A study in Los Angeles interviewed mothers of more than 200
children with brain cancer and close to 300 controls. It reported that use
of flea/tick products in the home was associated with increased risk of brain
cancer, particularly for children less than five years of age. The odds ratio
was 1.7 and 95% confidence interval was from 1.1 to 2.6 (12).

·A study in Europe that looked at 260 children with brain cancer
and similar children without the disease found that the risk of disease was
higher for children whose parents worked in agriculture or in jobs involving
automotive vehicles. This study also found that children with brain cancer
were more likely to have mothers who worked in jobs involving use of solvents
(13).

·A study in California and Washington interviewed parents of
540 children with brain cancers and parents of more than 800 other children
who were similar but did not have the disease. The study found that children
with brain cancer were more likely than other children to have had parents
who worked in the chemical industry (14).

·A small 1993 study reported an association between childhood
brain cancer cases in Missouri children and the use of pesticides in and around
the home. Compared to healthy children, brain cancer was nearly five times
more likely for children treated with Kwell shampoo, which contains the cancer-causing
insecticide lindane, to control head lice; five times as likely if parents
used pest strips containing the insecticide DDVP; and five times as likely
if they used flea collars on pets (15).
Because this was a small study with only 45 cases, the results were regarded
as preliminary.

·An early, small, exploratory study in 1979 reported that children
diagnosed with brain tumors in the Baltimore area were more than twice as
likely to have been exposed to insecticides during household exterminations
than children without cancer (16,
17).